The invention relates generally to the field of laminates such as are widely used to make printed circuit boards. In one application, the invention is applied to a composite material used as a substrate for such circuit boards, designated CEM-1. These have a paper core which has been impregnated with epoxy resins and then covered with woven glass cloth which also has been impregnated with epoxy resins.
The generally recognized types of laminates are discussed in Printed Circuits Handbook, Coombs ed., Third Edition, McGraw-Hill Book Co., 1988. The lowest cost materials typically use phenolic resin impregnated paper (FR-2) and are used where the cost is more important than the electrical and physical performance. FR-3 is a paper composite which has been impregnated with epoxy resins rather than phenolic resins. CEM-1 is a composite which is more expensive than the FR-2 and FR-3 materials, but which provides improved electrical and physical properties. For CEM-1 an epoxy resin is used to coat paper as in FR-3, but the core is covered with glass fiber reinforced epoxy resins outer layers. It has many applications, including television sets.
Circuit boards produce epoxy resin dust when they are punched, cut, or drilled during fabrication of printed circuit boards. This is particularly true for CEM-1 circuit boards since holes are punched in them and the impregnated paper reinforcing material is brittle. Dust is undesirable for various reasons, but particularly because it affects the precision with which circuit patterns are made. The present invention provides a means to significantly reduce the amount of dust produced, with the attendant advantages in manufacturing printed circuit boards.